This invention relates to the polymerization of norbornene derivatives such as dicyclopentadiene. The invention further relates to a catalytic system suitable for use in processes for the polymerization of norbornene derivatives.
U.S. Pat. No. 4,020,254 discloses a process for ring-opening polymerization of cycloolefins using a catalyst comprising
(a) a transition metal salt selected from tungsten halides and tungsten oxyhalides,
(b) a compound selected from dialkylaluminum halides, alkylaluminum sesquihalides and alkylaluminum dihalides, and
(c) an alkoxysilane.
More particularly, compounds are proposed of the formula RO--SiR'.sub.3, wherein R is CH.sub.3 -- or Y--CH.sub.2 --CH.sub.2 --, Y is hydrogen, halogen, nitrile, C.sub.1-4 alkoxy, R' is a methyl or ethyl radical, and the molar ratios of (a)/(b)/(c) are within the range of 1/0.5-10/0.5-3.
U.S. Pat. No. 4,481,344 discloses a process using a two-part tungsten-based metathesis catalyst system for preparation of a thermoset polymer of dicyclopentadiene units wherein a halogen-containing hydrocarbyl additive is incorporated. The hydrocarbyl additive is included in one of a plurality of reactant streams containing dicyclopentadiene, and contains at least one trihalogen-substituted carbon atom or at least one activated halogen atom. The halogen-containing hydrocarbyl additive is selected from chloroform, carbon tetrachloride, 1,1,1-trichloroethane, hexachloropropane, hexachloroacetone, ethyl trichloroacetate, alpha,alpha,alpha-trichlorotoluene, allyl chloride, allyl bromide, benzyl chloride and hexachlorocyclopentadiene.
The tungsten catalyst is made soluble in the monomer suspension stream by the addition of a small amount of an alcoholic or a phenolic compound. Suitable phenolic compounds are disclosed to be phenol, alkyl phenols and halogen-containing phenols, with tert-butyl phenol, tert-octyl phenol and nonyl phenol being most preferred.
British Patent Application No. 2,005,280 discloses a method for the preparation of random copolymers of dicyclopentadiene and a compound selected from cyclopentene, cyclooctene, 1,5-cyclooctadiene and 1,5,9-cyclododecatriene by the use of a catalyst system comprising
(a) tungsten hexachloride;
(b) an organosilicon compound of the general formula R.sub.4-n Si(y).sub.n in which the R substituents are selected from alkyl, cycloalkyl, aryl and aralkyl radicals, Y represents either a hydroxy group or a vinyl radical, and n is 1 or 2;
(c) a di-n-alkylether or a phenyl-n-alkylether; and
(d) an organo tin compound represented by the general formula ##STR3## in which R.sup.a, R.sup.b, R.sup.c and R.sup.d are selected from n-alkyl, phenyl and vinyl radicals.
Japanese Patent Application No. 53103000 discloses a process for the preparation of ring-opened polymers by ring-opening polymerization of norbornene-type derivatives containing polar or aromatic hydrocarbon groups and/or norbornadiene derivatives and cycloolefin compounds optionally in the presence of unsaturated polymers containing C--C bonds, using a catalyst system obtained from (a) organic metal compounds containing metals selected from Group IVB or IVA metals and (b) the product of the reaction of (1) the reaction product formed by reaction of an oxide of tungsten and/or molybdenum and a Lewis acid and (2) a silanol compound of formula R.sub.4-n Si(OH).sub.n, wherein R is halogen, alkyl having less than 15 carbon atoms, aryl or alkoxy, and n=1, 2 or 3.
European Patent Specification No. 0084888 relates to a process for the manufacture of a thermoset homopolymer by combining a first reactant stream containing the activator of a metathesis-catalyst system and a second reactant stream containing the catalyst of the metathesis-catalyst system, at least one of which streams contains dicyclopentadiene to form a reaction mixture and immediately injecting the reaction mixture into a mold where polymerization occurs. The catalyst may be a tungsten-containing compound which can be solubilized by the addition of a small amount of a phenolic compound. Suitable phenolic compounds include phenol, alkylphenols and halogenated phenols, with tert-butylphenol, tert-octylphenol and nonylphenol being most preferred. The starting dicyclopentadiene for this process must be essentially pure.
European Patent Application No. 0222432 relates to a process for the bulk polymerization of dicyclopentadiene by contacting it with a catalyst system comprising (i) a tungsten compound containing a phenyl group carrying a bulky alkyl group and (ii) an organic thin compound containing one hydrogen atom bound to the tin atom. This process has as advantages that the starting dicyclopentadiene need not be essentially pure and that the catalyst is more stable and less sensitive to oxygen.
The processes described above can be applied in a reaction injection molding (RIM) process. A RIM process involves mixing of two or more low-viscosity streams of components of a catalyst system dissolved in the monomer to be polymerized and injecting the combined streams into a mold where the monomer polymerizes to form a solid infusible mass.
One requirement to be met for a RIM process is a catalytic system which produces a high polymerization rate. Moreover, it is desirable that the polymerization start at a temperature in the range of from 25.degree. to 90.degree. C., so that the compounds of the catalytic system can be mixed at ambient temperature, and that after slight heating of the mixture the exothermic polymerization is initiated.
Due to the modern requirements of such RIM processes there is still a strong need to further enhance the rate of polymerization of dicyclopentadiene alone or in combination with other related cycloalkadiene comonomers, such as norbornene derivatives.
Therefore it is an object of the present invention to enhance the rate of polymerization of dicyclopentadiene, optionally blended with other norbornene derivatives such as cycloalkadiene or cycloalkene comonomers, by using a more active catalytic system.